Development Of A Bionic Scallop Robot Based On Dual-jets Propulsion

Utilizing the underwater bionic jet robot is one of the important technical approaches to exploit ocean resources and maintain the security of marine territories.However,the biological counterparts of the existing bionic jet robots are mainly mollusks in the class of cephalopods,such as cuttlefish,octopus,and squid,whose jet propulsion methods are mostly single-hole jet propulsion.Scallop is a bivalve organism that uses a dual-hole jet propulsion mode to move that has good mobility.The development of a scallop inspired robot can enrich the research of underwater bionic robots and provide a new jet propulsion mechanism for underwater bionic robots.Based on the study of the shape,opening and closing mechanism and movement mechanism of scallops,a computational fluid dynamics method is introduced to construct the numerical calculation platform of scallops' hydrodynamics.Built upon the calculation results,this thesis focuses on the structure design and configuration optimization of the bionic scallop robot.The theoretical models of the robot energy consumption,movement speed,and movement efficiency are established,with which the relationship between structural parameters and system movement speed is studied.An experimental platform is then built to comprehensively study the effect of shell size,the shape of supporting plate,and the opening and closing frequency and amplitude on the scallop robot's propulsion and steering performance.The experimental results show that the scallop robot can achieve high maneuverability,such as fast swimming and turning in situ.The main research contents are as follows:(1)Bionics research on scallops.Bionics research includes morphological bionics,physiological bionics and motion bionics.Among them,morphology focuses on exploring the morphological characteristics of scallop shells and muscle systems;physiology mainly studies shell opening and closing mechanism,unidirectional flow mechanism of water flow and scallop steering mechanism;motion bionics research uses a motion camera system to record scallop shells by building an experimental platform,to explore the law of important parameters such as the opening and closing speed and acceleration of the shell,the linear movement speed of the scallop,and the angular velocity change during the turning process.(2)Numerical research on scallops.Computational fluid dynamics analysis of scallops is carried out.According to the coupling law of the shell opening and closing movement and the flow field,a bionic propulsion dynamic mesh analysis algorithm is designed,a parameterized model of the shell is built,and the change law of the propulsion force of the shell with different appearances,grooves,cambers or other structures is explored,to verify the effectiveness of the groove structure in reducing the movement resistance of the shell.A parameterized model of the scallop robot is established,visually displaying the water flow velocity field and eddy current field of the robot's three motion stages.Subsequently,the pressure distribution on the inner and outer surfaces of the robot is obtained,and the rationality of the model is verified through numerical calculation.The propulsion process of the scallop robot under different opening and closing strategies is computed and analyzed.The variance of the resultant force on the scallop robot is obtained and compared with the real scallop.(3)Structural design and configuration optimization of the bionic scallop robot.The structure design of the scallop robot shell system,velum muscles,steering system and driving system is completed,and the optimization design of the scallop robot configuration is conducted with the experimental testing and simulation analysis.Based on the bionic research of the scallop shell,the robot shell with groove structure is designed to restore the real scallop shell shape;the artificial velum muscles that are iteratively designed can realize the unidirectional flow of water and verify the one-way permeability effect of the velum muscles through experiments.The steering system can adjust the size of the jet orifice.The drive system configuration optimization is carried out based on Adams kinematics simulation,and the key factors of the opening and closing speed modulation and the average and instantaneous opening and closing ratio of the robot,and the optimal structure design of the supporting plate is finally obtained.(4)Modeling and analysis of scallop robot movement.Through the research and analysis of the theoretical fluid mechanics of the scallop robot,a set of energy consumption models of the scallop robot that integrates the shell inertial motion,the external fluid flow response,the pressure difference between the internal and external fluids,and the spring contraction,is established.The three motion stages of robot opening,closing and sliding are analyzed,and the scallop robot motion speed model is obtained.The relationship between the scallop robot motion speed and its dimensions,opening and closing strategy,opening and closing range and other factors is achieved.A motion efficiency estimation model is established for the absorbing water from the front side and the absorbing water from the rear side,and a comparative analysis of the efficiency of the two propulsion methods is conducted.(5)Experimental analysis of scallop robot movement.The robot configuration optimization based on experimental analysis is carried out,and the propulsion performance is improved by changing the parameters such as the bending stiffness and height of the artificial velum muscles,the size of the jet port,the length of the shell,the frequency and amplitude of the opening and closing movement,and the opening and closing strategy.Exploring and experimentally assessing the optimization of steering effect to obtain the optimal parameter design of the robot.The final experiment shows that the scallop robot can move at the maximum average speed and instantaneous speed of 3.4 and 4.65 body length/second,respectively.In addition,on the basis of the calculation and experiment results the movement speed model,a comparative analysis of the movement speed theoretically and experimentally is carried out to verify the accuracy and reliability of the movement speed theoretical model.The steering strategy of the robot is formulated and its steering ability is experimentally analyzed,and the relationship between the turning radius and the size of the jet port is further quantified.The experimental results show that the scallop robot can achieve high maneuverability such as in-situ steering.The scallop robot proposed in this thesis provides a brand new idea for underwater bionic robots,laying the foundation for the development of bionic porous jet thrusters in the future.In terms of jet propulsion and opening and closing actions,it is also helpful to understand the movement mechanism of biological scallops.